Pressure-sensitive appear, heat-sensitive paper, light- and pressure-sensitive paper, electric heat-sensitive paper, a heat-sensitive transfer paper, and the like are well known as recording materials using a colorless electron donating dye and an electron accepting compound. They are disclosed in detail, for example, in British Pat. No. 2,140,449, U.S. Pat. Nos. 4,480,052, 4,436,920, 4,539,578, 4,523,205, 4,479,138, 4,531,140 and 4,471,074, Japanese Patent Publication No. 23922/85, Japanese Patent Application (OPI) Nos. 71191/73, 179836/82, 123556/85 and 123557/85 (the term "OPI" used herein means a published unexamined Japanese patent application).
A recording material must have properties such that (1) color densities and color sensitivities should be sufficient, (2) fog formation should not take place at 65.degree. to 70.degree. C., and (3) light-fastness of colored images should be sufficient.
Recently, many efforts have been made to improve the above properties, and extensive research has been done.
The inventors of the present invention have found that certain compounds are effective to improve the above properties.